Microwave treated water soluble and amide functionalized single walled carbon nanotubes have been investigated using femtosecond degenerate pump-probe and nonlinear transmission experiments. The time resolved differential transmission using 75 femtosecond pulse with the central wavelength of 790 nm shows a bi-exponential ultrafast photo-bleaching with time constants of of 160 fs (130 fs) and 920 fs (300 fs) for water soluble (amide functionalized) nanotubes. Open and closed aperture z-scans show saturation absorption and positive (negative) nonlinear refraction for water soluble (amide functionalized) nanotubes. Two photon absorption coefficient,beata ~250 cm/GW (650 cm/GW) and nonlinear index, gamma ~ 15 cm^2/pW (-30 cm^2/pW) are obtained from the theoretical fit in the saturation limit to the data for two types of nanotubes.
@article{arxiv.0807.1441,
title = {Ultrafast switching time and third order nonlinear coefficients of microwave treated single walled carbon nanotube suspensions},
author = {N Kamaraju and Sunil Kumar and B. Karthikeyan and Bhalchandra Kakade and Vijayamohanan K. Pillai and A. K. Sood},
journal= {arXiv preprint arXiv:0807.1441},
year = {2008}
}